Methods and apparatus for freeing stuck tools



Sept. 19, 1967 E. R LE BLANC 3,342,266

TUCK TOOL- METHODS AND APPARATUS FOR FREEING Sheet 1 2 Sheets Filed June 21 fo waro v [65/0/76 INVENTOR.

ATTOR/V% Sept. 19, 1967 E. R. LE BLANC METHODS AND APPARATUS FOR FREEING STUCK TOOLS Filed June 21, 1965 2 Sheets-Sheet 2 INVENTOR.

United States Patent 3,342,266 METHODS AND APPARATUS FOR FREEING STUCK TOOLS Edward R. Le Blane, Houston, Tex, assignor, by mesne assignments, to Schlnmberger Technology Corporation,

Houston, Tex., a corporation of Texas Filed June 21, 1965, Ser. No. 465,465 6 Claims. (Cl. 166-46) ABSTRACT OF THE DISCLOSURE This application discloses methods and apparatus for freeing a tool-supporting cable which has become securely engaged against the sidewall of a borehole. More particularly, the application discloses an elongated tubular member adapted to receive a suspension cable and to be dispatched downwardly thereon to the point at which the cable first engages the borehole wall. Gripping members are provided in the tubular tool to grip the cable and prevent upward movement of the tool in relation to the cable. Thus, in practicing the disclosed methods, by alternately tensioning and relaxing the cable, the tubular member is worked downwardly to separate the cable from the borehole wall and free it.

Accordingly, as will become more apparent, this invention relates to methods and apparatus for freeing tools that have become lodged in a borehole; and, more particularly, to methods and apparatus for disengaging a tool-supporting cable from the sidewall of a borehole.

In those Well completion operations conducted with a tool suspended from a wire line or electrical cable, it is not too uncommon for the tool to become lodged in some manner in the borehole during the operation. For example, movement of a tools suspension member often cuts elongated semi-circular recesses or so-called keyseats into projections along the borehole. Not too infrequently, such a keyseat is made along a portion of a borehole traversing a fairly permeable formation interval that has a formation pressure substantially lower than the hydrostatic pressure of the well control fluid. Should the suspension member enter such a keyseat, the hydrostatic pressure acting on the effective longitudinal cross-sectional area of the suspension member will press it into the keyseat. It is well known that the cable can become effectively sealed in the keyseat by the mudcake along the borehole walls to cause what is known as difierential sticking. Thus, if the pressure differential and the effective crosssectional area of the co-engaged surfaces are great enough, the suspension member will be held in the keyseat with such force that it can no longer be moved. It will be realized, of course, that such an accident may occur Whether the suspension member is an electrical cable with one or more conductors therein or is merely a suspension cable or some other flexible suspension member. Accordingly, the term cable as employed hereinafter will be understood to describe any flexible suspension member used to suspend a well tool Within a borehole.

It is, of course, not always possible to free a stuck cable by merely pulling on it. For example, if the cable has an average tensile strength of 12,000-lbs. and 8,000- lbs. of the cable is within the borehole above the point where the cable is stuck, a holding force of only 4,000-

lbs. would prevent the retrieval without parting. In 2 deep well, this would not at all be too uncommon should a sufiicient length of cable become difierentially stuck against the wall of the borehole. Moreover, it is not necessary for the cable to be so tightly held that it can not move even longitudinally. For, it a keyseat is particularly deep, engagement of the upper end of a tool with the lower end of the keyseat will resist an upward pull With sufificient force that it cannot be freed without parting the cable.

Heretofore, it has been customary to employ a so-called cut-and-thread procedure to free a stuck cable. In this procedure, the cable is first severed at the surface and the free ends are passed through a joint of drill pipe and temporarily reconnected. The joint is then lowered into the well and halted with the upper end near the rotary table. The cable is disconnected and its free ends are passed through a second joint of drill pipe before it is coupled to the first joint. The coupled joints are then lowered until the upper end of the second joint reaches the rotary table and the cable is again disconnected. Thus, by successively disconnecting and reconnecting the temporary cable connection, a drill string is progressively assembled and lowered around the cable. By continuing to add additional joints in this manner, it will be realized that when the lowermost end of the string reaches the stuck point, it will wedge the cable out of the keyseat and break the sealing engagement there-between as the drill string is lowered further. Once the cable has been successfully dislodged, it will, of course, be necessary to reverse the above-described procedure to remove the cable tool from the borehole. It will be appreciated that this procedure is extremely slow and tedious and expends a considerable amount of rig time.

Accordingly, it is an object of the present invention to provide new and improved methods and apparatus for releasing a well tool suspension member that has become lodged against a wall surface within a borehole.

This and other objects of the present invention have been accomplished by first tensioning the suspension cable of the well tool and selectively clutching a rigid member to an intermediate point on the cable above the keyseat to interpose the member between the Wall of the borehole and cable. Thereafter, by relaxing the cable above the intermediate point, the rigid member will be carried downwardly along the keyseat as the taut cable portion below the intermediate point relaxes. Apparatus for practicing the present invention is comprised of an elongated rigid member adapted for juxtaposition with a suspension cable and having selectively operable cable-gripping means on its upper portion.

The novel features of the present invention are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation together with further objects and advantages thereof, may best be understood by way of illustration and example of cartain embodiments when taken in conjunction with the accompanying drawings, in which:

FIGS. 1-3 are successive views illustrating the practice of the present invention;

FIG. 1A is a cross-sectional view taken along the line 1A1A of FIG. 1;

FIG. 4 is a cross-sectional view showing one embodiment of apparatus arranged in accordance with the prin-v ciples of the present invention;

FIGS. 5 and 6 are cross-sectional views taken respectively along the lines 55 and 6-6 of FIG. 4; and

FIG. 7 is an isometric view of one of the elements depicted in FIG. 4.

Turning now to FIG. 1, a well tool 10 is shown dependently suspended in a borehole 11 from a suspension cable 12. A portion of the cable 12 has contacted a sidewall of the borehole 11 and become lodged in a keyseat 13 (FIG. 1A) adjacent to an earth formation 14. To illustrate the present invention, it is assumed that the hydrostatic pressure of the well control fiuids 15 has pressed the cable into the keyseat 13 with a force so great that the cable cannot be safely released by pulling. Thus, once it has been determined that the cable 12 is firmly stuck, a cable-releasing tool 16 employing the principles of the present invention is loosely coupled to the cable at the surface of the ground and dispatched downwardly thereon into the borehole 11.

Once the cable-releasing tool 16 has reached the position shown in FIG. 1 to engage the sidewall of the borehole 11, a substantial tension force 17 is applied to the cable 12 from the surface of the ground. With the cable 12 being firmly lodged within the keyseat 13, it will be appreciated that the full length of the free portion 18 of the cable 12 above the so-called stuck point will elongate in response to the applied tension force 17. For a given cable, this elongation will be directly proportional to the applied tension force 17 as well as to the overall length of the free cable portion 18. Moreover, the amount that any incremental part of the free portion 18 elongates will be directly proportional to the ratio of the length of that incremental part to the overall length of the free cable portion. The total applied tension force 17 will, of course, be uniform along the total length of the free cable portion 18.

Accordingly, as seen in FIG. 1, the free cable portion 18 above the stuck point will be elongated a finite distance by the tension force 17 on the cable. It will be appreciated, of course, that the weight of the cable-releasing tool 16 can be utilized to hold it stationary. As the free cable portion 18 is stretched, it will elongate upwardly relative to the cable-releasing tool 16. Then, while the tension force 17 is maintained, selectively operable cablegripping means (not shown) on the cable-releasing tool 16 operate to securely grip the point on the free cable portion 18 that is immediately adjacent thereto. It Will be appreciated that by gripping the stretched free cable portion 18 at this intermediate point while the cable is held in tension, the intermediate point of gripping will return to its normal relaxed lower position whenever the cable 12 is relaxed. Moreover, the tension force 17 is, in effect, stored as a tensile force in the lower cable portion 19.

Accordingly, as best seen in FIG. 2, whenever the cable 12 is relaxed at the surface, this tensile force stored in the lower cable portion will be transmitted to the cable- -releasing tool 16 to pull it downwardly. This downward force will tend to slide the cable-releasing tool 16 along the sidewall of the borehole 11 and, in so doing, peel at least part of the lower cable portion 19 out of the keyseat 13 and away from the sidewall.

It will be realized, of course, that upon relaxing the cable 12 at the surface, the downward travel of the cablereleasing tool 16 will be at least equal to the distance which the lower cable portion 19 below the cable-gripping means was elongated by the tension force 17. Although this distance may be only a matter of inches, at least that length of cable portion 19 will be freed from contact with the sidewall of the borehole 11. In practice, however, it has been found that the weight of a heavy cable-releasing tool will often carry it much further downwardly along the cable 12 once the tool 16- begins to move. It will be understood, of course, that should this first tensioning operation be unsuccessful in freeing the well tool 10, it is necessary only to retension the cable 12 and repeat the operation. Thus, by alternately tensioning and relaxing the cable 12, the cable-releasing tool 16 will be moved progressively downwardly until the entire stuck portion of the cable has been freed from the keyseat 13.

As best seen in FIG. 3, once the cable-releasing tool 16 has been moved downwardly sufl'iciently far to shift the stuck portion of the cable 12 laterally out of the keyseat 13, the well tool 10 will be freed. It should be noted that although the cable-releasing tool 16 will eventually come to rest on top of the well tool 10, this will not prevent further use of the well tool. Then, whenever the well tool 10 has completed its function, it can be retrieved in the usual manner along with the cable-releasing tool 16.

Turning now to FIGS. 4-7, several views are shown of one embodiment of a cable-releasing tool 21 employing the principles of the present invention. As best seen in FIG. 4, the cable-releasing tool 21 is comprised of an elongated rigid body 22 having a longitudinal bore 23 through which a cable 24 may be passed. One or more cable-gripping means 25 and 26 are mounted near the upper end of the body 22 and arranged to securely grasp the cable 24 received in the longitudinal bore 23.

As seen in FIG. 4, the cable-gripping means 25 and 26 may take the form of one or more pairs of wedgeshaped blocks or slips 27 confined within inwardly facing recesses 28 on opposite sides of the longitudinal bore 23. The outer face 29 of each slip 27 is tapered downwardly and inwardly for sliding engagement with the complementarily tapered rear wall 30 of its respective recess 28. To ensure a more positive gripping of the cable 24, teeth 31 may also be formed on the inner vertical face of each slip 27. A compression spring 32 having its ends respectively confined within aligned recessed bores 33 and 34 in the top wall 35 of each recess 28 and the upper face 36 of each slip 27 normally urges each slip downwardly and inwardly toward the cable 24. It will be appreciated, of course, that the springs 32 are so selected that the cable-engaging slips 27 cannot engage the cable 24 with sufficient force to prevent the relatively free downward travel of the cable-releasing tool 21 on the cable.

As best seen in FIG. 5, these slips 27 are preferably closely confined between the opposed side walls 37 and 38 of the recesses 23 to prevent lateral tipping of the slips. As further seen in FIGS. 5 and 7, the inner faces of the slips 27 are also preferably generally semi- .circular so the teeth 31 of the opposed slips can grip the cable 24 substantially around the full circumference of the cable.

To simplify the mounting of the cable-releasing tool 21 around the cable 24, the body 22 is made of separable longitudinal parts 22a and 22b with the cutting plane being through the bore 23 and between the opposed slips '27. As best seen in FIG. 6, longitudinally-spaced pairs of bolts 39 straddling the longitudinal bore 23 may be used as necessary to fasten the separable parts 22a and 22b together. Thus, it will be realized that the separable parts 22:: and 22b may be readily assembled and secured around the cable 24 without having to first sever the cable. A split wiping ring 40 may be disposed within a concentric counterbore 41 in the nose 42 of the body 22 to wipe away mud on the cable 24 as the cable-releasing tool is traveling downwardly thereon. Lateral fluid passages 43 are provided in the body 22 between the longitudinal bore 23 and the exterior of the body to prevent the cable/releasing tool 21 from itself becoming differentially stuck. If desired, a number of either circumferential or spiral grooves 43 can also be formed around the body 22 to provide fluid communication on all sides of the tool 21.

As a further concenience, it has been found advantageous to fabricate the body 22 of the cable-releasing "tool 21 in a number of tandemly coupled sections 22- 22. Although other coupling arrangements can be used,

it is quite satisfactory to employ an interlocking arrangement as depicted in FIG. 4. By consistently arranging the lower end of a section, such as 22 or 22", with depending fingers 43 having inwardly projecting lugs 44 and the upper end of a section, such as 22" or 22", with upwardly extending fingers 45 having outwardly extending lugs 46, it will be appreciated that the upper and lower sections 22' and 22" may be selectively coupled in tandem to one another or spaced apart by one or more intermediate sections 22".

Accordingly, where substantial weight is desired, several of these intermediate sections 22" can be coupled between the upper and lower sections 22 and 22". Moreover, it will be realized that as the overall length of the cable-releasing tool 21 is increased, the cablegripping means 25 and 26 will be spaced further above the keyseated portion of the cable 24. Thus, by lengthening this spacing, a given tension force will result in greater elongation of the lower cable portion below the cablegripping means 25 and 26.

Accordingly, when using the cable-releasing tool 21 depicted in FIGS. 4-7, to practice the methods of the present invention, the tool 21 is assembled at the surface around the stuck cable 12 by progressively assembling and joining the opposed separable parts 22a and 22b of each section 22'22"' to one another around the cable. Once the cable-releasing tool 21 has been assembled, it is released and allowed to free-fall on the suspension cable 12 and come to rest where it will.

Then, either before or after the cable-releasing tool 21 has come to rest somewhere above the stuck point of the cable 12, the upwardly directed tension force 17 is applied to stretch the cable. As the free cable portion 18 elongates, it is free to move upwardly relative to the stationary cable-releasing tool 21. Accordingly, as the cable 12 moves upwardly, the slips 27 will be urged upwardly along the inclined walls 30 of the recesses 28 and against the bias of the springs 32. Then, when the cable 12 has been tensioned, the springs 32 will urge the slips 27 downwardly and into gripping engagement with the cable. It will be recognized, of course, that when tension is removed from the cable 12, the lower portion 19 of the cable 12 between the cable-gripping slips 27 and keyseat 13 will be prevented from moving downwardly relative to the tool 21 by the wedging action of the slips. Thus, when the cable 12 is relaxed at the surface, the stored tensile force in the lower portion 19 of the free cable portion 18 will be transmitted through the slips 27 to the cable-releasing tool 21 to carry it downwardly along the keyseat 13 and sidewall of the'borehole 11. If the first operation does not succeed in completely freeing the cable 12 from the keyseat 13, it will be necessary only to retension the cable 12 so as to re-engage the slips 27 and repeat the operation as many times as necessary.

Accordingly, it has been shown that the present invention provides new and improved methods and apparatus for releasing a keyseated suspension cable in the borehole. Moreover, the present invention has provided ap paratus cooperable with a suspension cable for harnessing its natural resilience as a motive force to free the cable should it become keyseated in a borehole.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects and, therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of this invention.

l What is claimed is:

1. A method for freeing a well tool suspension member stuck at a remote location and keyseated in a borehole wall comprising the steps of: tensioning the suspension member to produce elongation thereof; interposing a rigid member between the suspension member and borehole wall above the keyseat; clutching the rigid member to the tensioned suspension member for downwarc' movement therewith upon contraction of the suspensior member; and relaxing the suspension member to'release tensile forces therein for driving the rigid member downwardly between the keyseat and suspension member as the suspension member contracts.

2. A method for freeing a well tool suspension member stuck at a remote location and keyseated in a borehole wall comprising the steps of: interposing a rigid member between the suspension member and borehole wall above the keyseat, said rigid member having unidirectional clutch means thereon adapted for gripping the suspension member upon downward movement of the suspension member; tensioni-ng the suspension member to elongate the suspension upwardly relative to the stationary rigid member; relaxing the suspension member to release tensile forces induced therein and clutch the rigid member thereto for driving the rigid member downwardly between the keyseat and suspension members and, thereafter, alternating said tensioning and relaxing steps for progressively driving the rigid member along the keyseat until the suspension member is freed.

3. A method for dislodging a well tool stuck at a remote location in a borehole and suspended from a cable keyseated in a wall of the borehole comprising the steps of: dropping a rigid member slidably engaged with the cable and having unidirectional cable-gripping means thereon into a stationary position above the keyseat and between the cable and borehole wall, said cable-gripping means being operable to couple the rigid member to the cable upon downward movement of the cable relative thereto; pulling the cable upwardly relative to the rigid member to elongate the cable and induce tensile forces in the cable; relaxing the cable to release the tensile forces and couple the rigid member to the cable for driving the rigid member downwardly along the keyseat between the cable and borehole wall; and, thereafter, alternating said pulling and relaxing steps for progressively driving the rigid member along the keyseat until the cable is freed therefrom.

4. A well tool comprising: an elongated rigid body having a longitudinal passage therethrough adapted to receive a well tool suspension member; means on said body and facing said passage adapted for gripping a well tool suspension member therein upon downward movement of the suspension member relative to said body; and passage means on said body for equalizing fluid pressures between opposite outer longitudinal surfaces of said tool including at least one lateral passage between said surfaces.

5. A well tool comprising: a plurality of elongated rigid bodies, each of said bodies having a longitudinal passage therethrough adapted to receive a well tool suspension member; means for tandemly coupling said bodies to one another with said longitudinal passages in coincidental alignment; means on one of said bodies and facing said longitudinal passage therein adapted for gripping a well tool suspension member therein upon downward movement of the suspension member relative to said tool; and, passage means on said body for equalizing fluid pressures between opposite outer longitudinal surfaces of said tool including at least one lateral passage between said surfaces.

6. A well tool comprising: a plurality of elongated bodies having a longitudinal passage therethrough adapted to receive a well tool suspension member, each of said bodies including a plurality of substantially similar elon gated members having mating surfaces with a longitudinal groove therein and adapted to be joined together to form one of said bodies and means for joining said members to assemble said bodies; means for tandemly coupling said bodies to one another with said longitudinal passages in coincidental alignment; means on one of said bodies and facing said longitudinal passage therethrough adapted for gripping a well tool suspension member therein upon downward movement of the suspension member relative to said tool; and passage means on at least one of said bodies for equalizing fluid pressures between opposite outer longitudinal surfaces of said tool including at least one lateral passage between said surfaces.

References Cited UNITED STATES PATENTS 2,794,619 6/1957 Lawrence et al 166-54.6 3,146,611' 9/1964 Fox 175321 CHARLES E. OCONNELL, Primary Examiner.

JAMES A. LEPPINK, Assistant Examiner. 

1. A METHOD FOR FREEING A WELL TOOL SUSPENSION MEMBER STUCK AT A REMOTE LOCATION AND KEYSEATED IN A BOREHOLE WALL COMPRISING THE STEPS OF: TENSIONING THE SUSPENSION MEMBER TO PRODUCE ELONGATION THEREOF; INTERPOSING A RIGID MEMBER BETWEEN THE SUSPENSION MEMBER AND BOREHOLE WALL ABOVE THE KEYSEAT; CLUTCHING THE RIGID MEMBER TO THE TENSIONED SUSPENSION MEMBER FOR DOWNWARD MOVEMENT THEREWITH UPON CONTRACTION OF THE SUSPENSION MEMBER; AND RELAXING THE SUSPENSION MEMBER TO RELEASE TENSILE FORCES THEREIN FOR DRIVING THE RIGID MEMBER DOWNWARDLY BETWEEN THE KEYSEAT AND SUSPENSION MEMBER AS THE SUSPENSION MEMBER CONTRACTS.
 4. A WELL TOOL COMPRISING: AN ELONGATED RIGID BODY HAVING A LONGITUDINAL PASSAGE THERETHROUGH ADAPTED TO RECEIVE A WELL TOOL SUSPENSION MEMBER; MEANS ON SAID BODY AND FACING SAID PASSAGE ADAPTED FOR GRIPPING A WELL TOOL SUSPENSION MEMBER THEREIN UPON DOWNWARD MOVEMENT OF THE SUSPENSION MEMBER RELATIVE TO SAID BODY; AND PASSAGE MEANS ON SAID BODY FOR EQUALIZING FLUID PRESSURES BETWEEN OPPOSITE OUTER LONGITUDINAL SURFACES OF SAID TOOL INCLUDING AT LEAST ONE LATERAL PASSAGE BETWEEN SAID SURFACES. 